using GB5Shared.DTO.Framework.Login;
using GB5Shared.Telemetry;
using Microsoft.Extensions.Logging;
using CRMSalesDAL.CustomCode.LeadScoring;
using CRMSalesDAL.CustomCode.LeadScoringConfig;

namespace CRMSalesBLL.LeadScoring;

/// <summary>
/// SalesMind AI Lead Scoring engine. Composite 0-100 score across the reference material's 4
/// scoring dimensions (Demographic Fit / Behavioral Signals / Engagement Level / Deal Readiness) —
/// but only 2 of the 4 have a real data source in this codebase today. This class computes those 2
/// honestly and renormalizes their configured weights against each other; it does NOT fabricate
/// values for the other 2. See <see cref="RecalculateLeadScoreAsync"/> for the full rule.
/// </summary>
public class LeadScoringBLL : ILeadScoringBLL
{
    private readonly ILeadScoringDAL _LeadScoringDAL;
    private readonly ILeadScoringConfigDAL _LeadScoringConfigDAL;
    private readonly ILogger<LeadScoringBLL> _Logger;

    // Default weights (25/30/25/20 for Demographic/Behavioral/Engagement/DealReadiness) used only
    // when no MLEADSCORINGCONFIG row exists yet — matches this entity's documented defaults.
    private const decimal DefaultDemographicFitWeight = 25m;
    private const decimal DefaultDealReadinessWeight = 20m;

    public LeadScoringBLL(
        ILeadScoringDAL leadScoringDAL,
        ILeadScoringConfigDAL leadScoringConfigDAL,
        ILogger<LeadScoringBLL> logger)
    {
        _LeadScoringDAL = leadScoringDAL;
        _LeadScoringConfigDAL = leadScoringConfigDAL;
        _Logger = logger;
    }

    /// <summary>
    /// Demographic Fit (REAL dimension): 100 if the Lead has a non-default SegmentId AND ICPId
    /// (both != -1), 50 if only one is set, 0 if neither.
    /// </summary>
    public static int ComputeDemographicFitScore(int segmentId, int icpId)
    {
        bool hasSegment = segmentId != -1;
        bool hasICP = icpId != -1;

        if (hasSegment && hasICP) return 100;
        if (hasSegment || hasICP) return 50;
        return 0;
    }

    /// <summary>
    /// Deal Readiness (REAL dimension): derived from the MAN score of the Lead's most recent OPEN
    /// Deal, if one exists — percentage of the 3 MAN criteria marked "Yes" (1): 0/33/67/100 for
    /// 0/1/2/3 "Yes" answers. 0 if no open Deal exists yet for this Lead (all 3 fields null).
    /// </summary>
    public static int ComputeDealReadinessScore(byte? manMoney, byte? manAuthority, byte? manNeed)
    {
        if (manMoney == null && manAuthority == null && manNeed == null)
            return 0;

        const byte yes = 1;
        int yesCount = (manMoney == yes ? 1 : 0) + (manAuthority == yes ? 1 : 0) + (manNeed == yes ? 1 : 0);

        return yesCount switch
        {
            0 => 0,
            1 => 33,
            2 => 67,
            _ => 100
        };
    }

    /// <summary>
    /// Composite score rule:
    /// <list type="bullet">
    /// <item>Demographic Fit and Deal Readiness are REAL — computed from live TLEAD/TDEAL data
    /// (see <see cref="ComputeDemographicFitScore"/>/<see cref="ComputeDealReadinessScore"/>).</item>
    /// <item>Behavioral Signals and Engagement Level are DEFERRED — Behavioral Signals has no
    /// website-visit/content-download tracking anywhere in this codebase yet; Engagement Level
    /// depends on the Interaction Journal, a future SalesMind pass not built yet. Both contribute
    /// 0, not a fabricated value.</item>
    /// <item>The two real dimensions' configured weights (from MLEADSCORINGCONFIG, or the
    /// 25/20 defaults if no config row exists) are RENORMALIZED against just their own combined
    /// weight — e.g. if Demographic=25 and DealReadiness=20 are the only real ones out of 100
    /// total configured weight, effective score = 25/(25+20) * DemographicScore +
    /// 20/(25+20) * DealReadinessScore. This avoids silently zero-weight-averaging against all 4
    /// configured weights, which would understate every real lead's score by design.</item>
    /// </list>
    /// </summary>
    public async Task<string> RecalculateLeadScoreAsync(int leadId, LoginDTO loginDTO, CancellationToken ct)
    {
        try
        {
            GB5Trace.Step("recalculate-lead-score", new { leadId });

            var input = await _LeadScoringDAL.GetLeadScoringInput(leadId, loginDTO, ct).ConfigureAwait(false);
            if (input == null)
                throw new Exception($"Lead {leadId} was not found.");

            var config = await _LeadScoringConfigDAL.GetLatestLeadScoringConfig(loginDTO, ct).ConfigureAwait(false);
            decimal demographicWeight = config?.DemographicFitWeightPercent ?? DefaultDemographicFitWeight;
            decimal dealReadinessWeight = config?.DealReadinessWeightPercent ?? DefaultDealReadinessWeight;

            int demographicScore = ComputeDemographicFitScore(input.SegmentId, input.ICPId);
            int dealReadinessScore = ComputeDealReadinessScore(
                input.LatestOpenDealMANMoney, input.LatestOpenDealMANAuthority, input.LatestOpenDealMANNeed);

            decimal totalRealWeight = demographicWeight + dealReadinessWeight;
            int compositeScore = totalRealWeight <= 0
                ? 0
                : (int)Math.Round(
                    (demographicWeight / totalRealWeight) * demographicScore
                    + (dealReadinessWeight / totalRealWeight) * dealReadinessScore,
                    MidpointRounding.AwayFromZero);

            await _LeadScoringDAL.UpdateLeadScore(leadId, compositeScore, loginDTO, ct).ConfigureAwait(false);

            _Logger.LogInformation(
                "Lead {LeadId} score recalculated to {Score} (DemographicFit={DemographicScore}, DealReadiness={DealReadinessScore}) by user {UserId}",
                leadId, compositeScore, demographicScore, dealReadinessScore, loginDTO.UserId);

            return $"Lead {leadId} score recalculated: {compositeScore}";
        }
        catch (Exception ex)
        {
            GB5Trace.MarkFailed("recalculate-lead-score-failed", ex);
            _Logger.LogError(ex, "RecalculateLeadScoreAsync failed for LeadId {LeadId}", leadId);
            throw;
        }
    }
}